Certain clinical and morphologic findings are described in 10 necropsy- diagnosed patients with solitary coronary ostium in the aorta. In addition, previously published data are summarized in 35 necropsy- diagnosed cases and in 52 angiographically-diagnosed cases of solitary aortic coronary ostium. On the basis of this information a simple and practical classification of this entity is presented. Of the total 97 cases analyzed, the presence or absence of associated coronary arterial narrowing by atherosclerotic plaque was known in 85. Of these 85 patients, 53 had absent or insignificant coronary luminal narrowing and 8 of the 53 (15%) had clinical or morphologic evidence of myocardial ischemia, a finding which can be attributed entirely to the presence of the coronary anomaly.